As is known, in side doors with an unframed upper edge, when the side door is closed and its glass is fully raised, the upper edge of the glass rests against a sealing element which is held in a fixed position by an upper side member forming part of the bodywork or the roof.
During the assembly of the door on the motor vehicle, the position of the upper edge of the glass with respect to the sealing element must be adjusted in such a way as to press the sealing element when the glass is raised with a deformation and/or pressure such as to ensure a water-tight seal, but not such as to make closing the side door difficult.
For this purpose, varying the position of a frame that supports the glass and that is arranged inside the door is known in the prior art. This frame has a hinged upper portion to allow the frame and, therefore, the glass, to tilt about an axis of adjustment that is substantially horizontal and parallel to the glass.
To stop the tilting, a lower portion of the frame carries a screw on which a nut is screwed. When the frame is made to tilt and the upper edge of the glass moves towards and away from the roof, the screw slides in a slot which is obtained in a fixed portion and is elongated in a tangential direction with respect to the axis of adjustment. Once a satisfactory adjustment has been achieved, the position chosen for the glass is held by tightening the nut on the screw against the fixed portion.
The adjustment procedure described above falls far short of being satisfactory as it does not enable the positioning of the upper edge of the glass in a precise and quick manner. The slot defines a maximum sliding stroke of about 10-12 millimeters, making it quite difficult for the screw to slide along the slot in a precise manner to find the correct angular position for the glass. Furthermore, once it has reached a satisfactory position, it is quite difficult to tighten the nut while at the same time keeping the screw firm in the slot.